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Why code in Node.js often get rejected by SoundCloud Phil Calçado - SoundCloud @pcalcado http://philcalcado.com Tuesday, October 1, 13

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2011: Phil zieht nach Berlin Tuesday, October 1, 13

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Tuesday, October 1, 13

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~ 200 million users / month > 11 hours of audio uploaded every minute Tuesday, October 1, 13

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Tuesday, October 1, 13

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http://bit.ly/15DToNK hiring @ SoundCloud Tuesday, October 1, 13

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Phone Code Review Interviews Offer Tuesday, October 1, 13

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Phone Code Review Interviews Offer Tuesday, October 1, 13

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challenge until late 2012 Tuesday, October 1, 13

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you can choose any language. 0 10 20 30 40 Ruby Java JavaScript (Node.js) C Clojure Scala % of submissions ~2011-2012 Tuesday, October 1, 13

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you can choose any language. 0 10 20 30 40 Ruby Java JavaScript (Node.js) C Clojure Scala rejected before interview invited for inverview Tuesday, October 1, 13

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new challenge Tuesday, October 1, 13

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you can choose any language. 0 7.5 15 22.5 30 Ruby Java JavaScript (Node.js) Go Clojure Scala % of submissions on the past ~1 year Tuesday, October 1, 13

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you can choose any language. 0 7.5 15 22.5 30 Ruby Java JavaScript (Node.js) Go Clojure Scala % of submissions on the past ~1 year Tuesday, October 1, 13

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you can choose any language. 0 7.5 15 22.5 30 Ruby Java JavaScript (Node.js) Go Clojure Scala rejected before interview invited for inverview Tuesday, October 1, 13

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you can choose any language. 0 7.5 15 22.5 30 Ruby Java JavaScript (Node.js) Go Clojure Scala rejected before interview invited for inverview WTF? Tuesday, October 1, 13

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http://bit.ly/J1aLNn don’t get me wrong we are all hipsters Tuesday, October 1, 13

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Tuesday, October 1, 13

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Not OO, not Functional... Just (bad) Procedural code. Tuesday, October 1, 13

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http://bit.ly/JiECRp Tuesday, October 1, 13

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we don’t need this complicated stuff. this is not java, you know. Tuesday, October 1, 13

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http://bit.ly/JiFSnq so how do we structure our app? Tuesday, October 1, 13

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what to use? (decent) procedures? Tuesday, October 1, 13

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what to use? objects? Tuesday, October 1, 13

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Tuesday, October 1, 13

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what to use? ...functions? Tuesday, October 1, 13

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http://bit.ly/JFbZt8 Tuesday, October 1, 13

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http://bit.ly/JFbZt8 “SICP and some of the Sussman & Steele "Lambda the ..." papers made a big impression on me years before, although I did not understand their full meaning then. Remember, I was recruited to "do Scheme" [...] My interest in languages such as Self informed a subversive agenda [...]. Likewise with first-class functions, which were inspired by Scheme [...]” Tuesday, October 1, 13

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http://bit.ly/JiEQYM Tuesday, October 1, 13

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http://bit.ly/JiF7ef going old school Tuesday, October 1, 13

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e.g. passing functions around Tuesday, October 1, 13

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we see a lot of this Tuesday, October 1, 13

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1st, we extract what is common Tuesday, October 1, 13

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then we refactor our functions Tuesday, October 1, 13

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and we send them as arguments Tuesday, October 1, 13

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e.g. closures not only for objects Tuesday, October 1, 13

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we see a lot of this Tuesday, October 1, 13

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we can keep writeComment as it is Tuesday, October 1, 13

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and we add a function with two closures Tuesday, October 1, 13

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and we add a function with two closures immutable Tuesday, October 1, 13

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and we add a function with two closures immutable mutable Tuesday, October 1, 13

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now we don’t need to pass in the kitchen sink Tuesday, October 1, 13

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e.g. functions all the way down Tuesday, October 1, 13

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we see a lot of this Tuesday, October 1, 13

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first we extract common protocol Tuesday, October 1, 13

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then we clean up our functions Tuesday, October 1, 13

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then we use them. Tuesday, October 1, 13

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then we use them. redundant? Tuesday, October 1, 13

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http://bit.ly/JiETnd Tuesday, October 1, 13

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our “framework”: 1 - Extract protocol in “combinators” 2 - Keep mutable state in closures Tuesday, October 1, 13

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no scary monads required Tuesday, October 1, 13

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there is plenty to learn from Tuesday, October 1, 13

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in the javascript community too Tuesday, October 1, 13

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phil calçado http://philcalcado.com @pcalcado www.soundcloud.com Tuesday, October 1, 13

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How to Design Programs - http://bit.ly/K0BfrL Structure and Interpretation of Computer Programs - http://bit.ly/K0BjYm The Art of the Metaobject Protocol http://amzn.to/K0BqU1 Purely Functional Data Structures http://amzn.to/JFn4KG Let Over Lambda - http://amzn.to/IMMkNO An Introduction to Lambda Calculi for Computer Scientists - http://amzn.to/IX8d1B All drawings are available as t-shirts from the awesome Diesel Sweeties - http://dieselsweeties.com/ Tuesday, October 1, 13